Biomass Energy Overview

From Thermal-FluidsPedia

Biomass energy refers to the energy of all products derived from living organisms. Just like fossil fuels, biomass is formed by the Sun which, through photosynthesis, converts carbon dioxide and water into organic matter. However, unlike fossil fuels that take millions of years to form, biomass can be produced in a short period of time. In fact, this is how the human body converts food into the energy it needs to perform daily tasks. Many of the materials we use and much of the by-products of our activities are biomass; they can be burned directly or converted into liquid and gaseous fuels such as methanol, ethanol, biogas and synfuel.

Although only a tiny fraction of the solar energy that reaches the earth is converted into biomass, it can fulfill all the world’s energy needs. Currently, biomass contribution to overall energy consumption is small. However, if energy contained in food is included, biomass provides about 15% of all the energy consumed in the world and, after oil, coal, and natural gas, is our fourth largest energy resource (a). Until the mid nineteenth century, wood provided 90% of energy used in the United States, before better coal technology and the discovery of petroleum reduced the demand for biomass. Today, about 3% of the US energy demand is supplied by biomass, mostly for residential heating and cooking in the form of firewood, but also indirectly as feedstock for the production of liquid and gaseous biofuels (1). Some developing countries, mainly China and India, satisfy as much as one third of their total energy needs from biomass.

Tires, pulp, paper, wooden products, foodstuff, rice husks, peanut shells, fruit pits and animal waste are all examples of biomass. Municipal solid wastes are, for the most part, derived from plants and other organic matter. Unfortunately, they contain a variety of other substances that are highly toxic and could pose a health hazard if burned; due to these toxic components many people do not consider them to be biomass.

Although biomass energy is renewable, it is not clean, and when burned, like other conventional fuels, it produces pollution. The emissions are lower, however. Furthermore, the carbon dioxide produced from the combustion of biomass offsets that used up during its formation, maintaining zero net production of this dangerous greenhouse gas.

In this chapter, we will discuss the mechanism for the formation of biomass, its resources, and its many applications.

When the earth was formed about 5 billion years ago, it was nothing more than a collection of extremely hot cosmic dust with no atmosphere. With time, these particles lumped together by the force of gravity forming an early atmosphere of mostly hydrogen and helium. This was followed by volcanic eruptions which produced water vapor, nitrogen, methane, sulfur, and a few other gases present in today’s volcanoes. No free oxygen was yet present. As earth cooled, water vapor turned into liquid, filling up oceans. Small amounts of oxygen gas appeared only after sun’s ultraviolet radiation broke up the water molecules. The condition was now just right for carbon dioxide and water to react through a process called photosynthesis, making the simpler organic compounds. As by-products, oxygen and ozone were also formed. As the atmosphere thickened, dinosaurs, birds, more complex animals, and eventually the primary form of man appeared.